Engine exhaust contains carbon monoxide (C0), hydrocarbons (HC) and nitrogen oxides (NOx) and other harmful gases, the three-way catalytic converter is a kind of conversion device that can convert these three kinds of harmful gases into harmless substances. The three-way catalytic converter is installed in the exhaust pipe and is similar in shape to a muffler. The outer cylinder is made of double-layer stainless steel plate, with asbestos fiber felt as heat insulation material in the sandwich. Inside the cylinder is a high-temperature-resistant ceramic carrier with dense honeycomb holes in the longitudinal direction (there are also other shapes, such as sphere, prismatic body, mesh partition, etc.), and the surface of which is sprayed with a very thin layer of platinum, rhodium and palladium active catalytic layer as a purifying agent (also known as a catalyst). catalyst).
The working principle
When the engine exhaust gas is discharged through the exhaust pipe, due to the catalytic effect of the purifying catalyst in the three-way catalytic converter, the activity of C0, HC and NOx is enhanced, and thus oxidation-reduction reaction is carried out, in which C0 is oxidized into the colorless and non-toxic C02 at a high temperature, and HC compounds are oxidized into H20 and C02 at high temperature, and NOx is reduced into N2 (nitrogen) and 02 (nitrogen). (nitrogen) and 02 (oxygen), so that the engine exhaust emissions can be purified.
Three, "three-way catalytic converter" blockage blockage failure performance
1, the first stage for the slight blockage stage. At this stage, chemical complexes are adsorbed on the catalyst surface. Only the exhaust gas purification function is reduced. The exhaust gas emission exceeds the standard.
2. The second stage is the moderate blockage stage: chemical complexes have accumulated to a certain extent on the catalyst surface, and the exhaust back pressure rises at this stage. Fuel consumption increases and power decreases
3. The third stage is the severe blockage stage. Due to the serious blockage, the working temperature of the three-way catalytic converter rises. In the front of the three-way catalytic converter to form a high-temperature sintering blockage.
4. High temperature sintering blockage. High-temperature sintering clogging is divided into two types: a metal sintering clogging. A carbon sintering coking blockage. It is determined by the fuel whether to use lead-containing, manganese-containing anti-explosive agents, this stage is characterized by a serious decline in power, often stalling, serious exhaust pipe burning red, and even cause spontaneous combustion of the vehicle.
Four, test to determine the blockage of the three-way catalytic system method:
In the three-way catalytic converter by its own working environment is very poor as well as its transformation performance characteristics of the impact of the use of the process there will be a variety of different failures. For example, due to the three-way catalytic converter clogging caused by the engine power decline, stalling or starting difficulties and exhaust gas exceeds the standard and other phenomena, is likely to interfere with our fault judgment.
1. Check whether the voltage of the front and rear oxygen sensors of the three-way catalytic converter is consistent. If it is the same, it means that the three-way catalytic converter is damaged, that is, it is clogged or burned because of the engine misfire to the three yuan.
2. Put your hand to the exhaust pipe to see if you can feel the airflow, if you can't feel it, it is clogged.
3. Take off the air filter. Press the gas pedal sharply in place. Look for black smoke coming out of the air filter.
4. Sense the temperature difference between the front and rear of the three-way catalytic converter to determine whether it is clogged.
5. When you test drive the car, you can't reach the maximum speed, and the acceleration is not good.
Fifth, the reasons for the blockage
1, gasoline: gasoline high sulfur content in the three-way catalytic converter is easy to form a chemical complex caused by the blockage. Poor oil quality, gum more gasoline easily cause three-way catalytic converter clogging. The use of leaded or manganese-containing anti-knock agent gasoline is likely to cause three-way catalytic converter clogging although China has strictly prohibited the use of leaded gasoline. But some areas of gasoline in the transportation and storage process of lead pollution is serious. Some small refineries in order to reduce costs, is still illegal to use leaded antiknock agent. Manganese-containing antiknock agent has been banned in developed countries, but most parts of China are still in use). The use of ethanol gasoline is easy to cause three-way catalytic converter blockage, ethanol gasoline is easy to form carbon deposits in the combustion chamber, at the same time, ethanol gasoline on the air intake system, the combustion system gel carbon has a flushing effect, flushing down the gel carbon is easy to form a three-way catalytic converter blockage.
2, motor oil: long-term use of motor oil containing sulfur and phosphorus antioxidants can easily cause three-way catalytic converter blockage.
3, the road: because the car in the acceleration, deceleration conditions produce incomplete combustion of the most. Therefore, driving on congested roads for a long time will easily cause the three-way catalytic converter to be clogged.
4, "nozzle, intake cleaning maintenance": due to the cleaning process will be flushed down a large number of gelatinous carbon. So it is easy to cause three-way catalytic converter clogging, which is also some vehicles in the "nozzle, intake cleaning maintenance" after the increase in fuel consumption.
5, turbo: with turbo vehicles are prone to three yuan catalytic converter clogging. This is mainly due to the driver's incorrect operation." Three-way catalytic converter" clogging is gradually formed, the generation of clogging is reversible, clogging can be reduced through chemical processes such as oxidation and gasification, but also through physical processes such as desorption and volatile components, gas-phase component evaporation and reduction.
Sixth, the solution
"Three-way catalytic converter" clogging is a very common problem, especially in cities with congested roads. The problem is also prominent in areas with poor fuel quality. Three-way catalytic converter" clogging not only seriously cause the vehicle fuel consumption increase, power down, exhaust exceeds the standard, more serious can make the exhaust pipe burn red, causing vehicle spontaneous combustion. For a long time, auto body shops have no effective means of preventing "three-way catalytic converter" clogging. There is no effective means of governance, for the blockage of the "three-way catalytic converter". Only take the method of replacement. Three-way catalytic converter price depends on with or without exhaust, without exhaust catalytic converter general regular price is 800-1200 factory price, but the 4S store to see to add money, if the regular 4S store in 2000 +.